Naturalists’ Notes

Arboretum naturalists lead tours and record their observations throughout the seasons, gathering a valuable phenological record of Arboretum events. These notes also offer visitors a wealth of information on what you can see and enjoy at any particular time of the year.

Curtis Prairie

June 18, 2017

White wild indigo

“What is so rare as a day in June?”, asked the poet James Russell Lowell. “Then, if ever, come perfect days.” We had one like that on Sunday. Our hike started and ended in summer sunshine, with dark clouds briefly visible to the west (but they moved away without doing any harm).

We began our tour in the Native Plant Garden, the system of small gardens that immediately surrounds the Visitor Center. It demonstrates, in a compact and accessible setting, the diverse plant communities of which there are larger examples in more remote areas of the Arboretum.

Generally, the prairie is in its blue-and-white phase (with touches of yellow predicting its next color wave). In fact, we even got a good look at a blue species of bird toward the end of our walk! More about that later. Florally speaking, it’s spiderwort (Tradescantia ohiensis) which furnishes the blue. Come to the prairie before noon for the most vivid view, as the blossoms close up early when it’s hot.

Within the Native Plant Garden we examined wild quinine (Parthenium integrifolium), white wild indigo (Baptisia alba), Canada anemone (Anemone canadensis), and a few early compass-plants (Silphium laciniatum) in flower. White wild indigo can be used to produce a dye, although I hear it’s not of as high quality as the Old World indigo. I still want to try the process, however. I have read that the dye bath is yellow; the blue color only appears after the fabric is removed from the solution and exposed to air.

A visitor asked about wild (poison) parsnip, so at the corner of the Curtis Prairie nearest the big metal sculpture, I pointed it out. Pastinaca sativa, as it is known to botanists, is coming into bloom. It looks like yellow Queen Anne’s-lace, but don’t pick it for any reason! The plant’s juice, when it contacts your skin and is exposed to sunlight, will cause chemical burns of varying severity. Blistering can occur. Many people have had accidental encounters with wild parsnip when mowing or weeding and have horror stories to tell.

In that same area we examined the white flowers of tall beard-tongue, or false foxglove (Penstemon digitalis). I offered my guests a hand lens for a closer look inside the tube-shaped blossoms. One sees immediately the reason for the “beard-tongue” name—the central stamen is prominent and fuzzy! The other four, which are actually the fertile ones, are smooth and curved like miniature whalebones.

Yet another white-flowered plant right nearby is common yarrow, or Achillea millefolium. The Greek hero Achilles is said to have carried this plant into battle to treat his soldiers’ wounds. It does have astringent or blood-stanching effects.

Even the shrubs currently blooming in the prairie have white flowers. Those would predominantly be gray dogwood (Cornus racemosa) and elderberry (Sambucus sp).

In the McCaffrey Oak Savanna, we found one common St. John’s-wort specimen rushing the season. Why do I say that? Because it’s not supposed to open until June 24—St. John’s Day—and here it was only the 18. (An older tradition held that it bloomed on the summer solstice, and ascribed witchcraft or pagan powers to the species. The early Catholic church rebranded it.)

Unfortunately the huge majority of St. John’s-wort that you will see in the Arboretum is a non-native, weedy variety—Hypericum perforatum. Many authorities go so far as to call it invasive. Still, it’s fun to demonstrate some of its interesting characteristics—tiny “perforations” (actually clear glandular spots which only look like holes) in the leaves, and the fact that crushing a (yellow) bud between one’s fingers yields a purplish liquid.

Our next cool sighting was on common milkweed (Asclepias syriaca). Dozens upon dozens of black aphids were darkening the tips of several plants. These are the black bean aphid—Aphis fabae. Despite its name, it utilizes many other plants, not just legumes.

Ants were hanging around on the lower stems of the infested milkweeds, indicating that the aphids were producing the sweet secretion referred to as “honeydew.” Ants—which feed on the excess honeydew—will actually defend the plant against aphid predators such as ladybugs. In fact, on one of the milkweed specimens, I spotted one ladybug who must have gotten past the guards. The whole food chain, right there!

We paid a quick visit to the rock honoring the late John T. Curtis, esteemed plant ecologist and botany professor, and proceeded to the great tree known as the Jackson Oak. A skeleton now, this white oak was named for Joseph W. Jackson—Arboretum booster par excellence—in 1963. Several apparent progeny grow around it.

I wanted to get out there because a few days earlier, driving out of the Arboretum, I had spotted an orangey blotch on the tree’s trunk. Did another branch break off? No, on a tree that has been dead for 15+ years, exposed wood would not be that fresh-colored; rather, it was a mass of fungal growth. That day I did not have time to go closer and look at the underside of the fungus, to try to make an ID.

Alas, by Sunday the mass had deteriorated enough that a certain identification still eludes me. Could have been Chicken of the Woods; could have been Orange Mock Oyster. Maybe it will regrow and I’ll be able to recheck.

As we strolled back toward the Visitor Center, we were treated to some great looks at an indigo bunting! He sang over and over, first from a small tree in the center of the prairie, then flying to a branch of the Jackson Oak, and making his final appearance at another small tree in the section of the prairie nearest the road. What a glorious iridescent blue these birds show in sunlight.

A few pale purple coneflowers have begun to open in the west portion of the Curtis Prairie. They are more easily seen from the interior trails—but do check carefully for ticks after you have ventured on those. At this time of year, brushing up against grassland plants carries some risk.

I had talked a bit about the science of ecological restoration, and our Arboretum’s pivotal role in same. One of my visitors asked how we have decided which era to restore to—since after all, over geologic time the landscape and ecosystem have changed considerably.

A very good and thoughtful question! Mostly the Arboretum strives to demonstrate the native Wisconsin communities immediately pre-European settlement—before agriculture and urbanization changed so much of the face of the land. We have used land survey records from the 1830s to guide the process.

Prairie, savanna, woodland, or wetland: there is always scenery to appreciate at the Arboretum.